1. Field of the Invention
The present invention relates to a bypass turbojet-engine thrust reverser. More specifically, the present invention relates to such thrust reverser comprising at least one pivotable hollow door.
2. Background of the Invention
A turbojet engine has a conduit at the rear of the fan for the purpose of channeling the so-called cold, bypass flow. The conduit consists of an inner wall enclosing the actual engine structure to the rear of the fan and an outer wall of which the upstream portion is continuous with an engine casing enclosing the fan. This outer wall is able to simultaneously channel the bypass flow and the primary flow in its downstream portion to the rear of the so-called hot, primary-flow exhaust, as regards mixed or confluent flows pods, for example. However, in other cases, the outer wall only channels the bypass flow, as regards the so-called separate-flows pods.
A wall also may be used to fair the outside of the engine, that is to say the outside of the engine casing enclosing the fan and the outside of the aforementioned outer wall, in order to minimize powerplant drag. This is particularly the case when the turbojet-engines project from the aircraft, for example, when suspended under the wings or mounted to the rear of the fuselage.
European patent document 0,822,327 describes an illustrative embodiment, shown in FIG. 1 of the attached drawings, of a thrust reverser with hollow doors that act as scoops. This thrust reverser is combined with a bypass turbojet-engine.
The thrust reverser consists of a movable sub-assembly and of a stationary structure. The movable sub-assembly consists of hollow doors 3 including a movable portion 2 which, when in the forward-thrust mode, constitutes part of an external cowling. The stationary structure 6 consists of an upstream portion 8 upstream of the doors 3, a downstream portion 7 downstream of the doors 3 and beams connecting the upstream portion 8 to the downstream portion 7. The stationary structure 6 is also a component of the external cowling.
The doors 3 are mounted along a circumference of the external cowling and are pivotable in a zone downstream of their side walls on the beams linking the downstream portion 7 to the upstream portion 8 of the stationary structure 6 located on either side of the doors 3. The side walls link the outer wall or panel 4 of the doors 3, which constitutes part of the external cowling in the forward thrust mode, to the inner part 5 of the doors 3, which constitutes part of the outer conduit wall.
The upstream portion 8 of the stationary structure comprises a fore frame that may be used to support means controlling the displacement of the doors 3 and illustratively consisting of linear actuators. These means controlling the displacement of the doors 3 also may be situated elsewhere on the periphery of the doors 3, for example downstream of the doors 3. In this case the control means may rest on the downstream portion 7 of the stationary structure 6.
When driven into a reverse thrust position, each of the doors 3 pivots in such a way that a door portion upstream of the pivot 9 will more or less completely obstruct the conduit while clearing a passage in the external cowling to allow channeling respective bypass flows 13 and 14 centrifugally relative to the conduit axis on one hand in an inner conduit or nozzle 10 formed by the structure of the door 3 and, on the other hand, between a deflection edge 12 and the outside of the outer panel 4 of the door 3. A downstream door part moves near the outside of the external cowling. The doors' angular position is adjusted to allow the flow to pass and to strongly reduce, even suppress forward thrust form this flow, and to generale a counter-thrust by producing an upstream-deflected flow component.
The geometric contour of the external cowling enclosing the thrust reverser must provide optimal flight aerodynamic performance. At the present time, this entails constricting the streamlines of the external thrust-reverser structure in the downstream direction of the external cowling. As shown in FIG. 1, the scoop door 3, with an upstream side pivoting centrifugally relative to the turbojet-engine axis, has an effective exhaust cross-section S2 of the inner conduit 10 which is less than an intake cross-section S1 of the inner conduit 10. As a result, the performance in thrust reversal mode is lowered because of the action of the flow 13b leaving the inner conduit 10 of the door 3 on the flow 14 between the deflection edge 12 and the outside of the outer door structure 4. One of the objectives of the present invention is to increase the aerodynamic performance of such scoop doors when in the thrust-reversal mode while still observing the above constraints.